113 lines
3.6 KiB
Groff
113 lines
3.6 KiB
Groff
.\" $NetBSD: minherit.2,v 1.21 2019/09/08 17:47:33 sevan Exp $
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.\"
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)minherit.2 8.1 (Berkeley) 6/9/93
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.\"
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.Dd September 8, 2019
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.Dt MINHERIT 2
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.Os
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.Sh NAME
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.Nm minherit
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.Nd control the inheritance of pages
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/mman.h
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.Ft int
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.Fn minherit "void *addr" "size_t len" "int inherit"
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.Sh DESCRIPTION
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The
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.Fn minherit
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system call changes the specified range of virtual addresses to have
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the inheritance characteristic
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.Fa inherit ,
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which determines how
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.Xr fork 2
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will map the region in the child process.
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The supported inheritance characteristics are:
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.Bl -tag -offset abcd -width MAP_INHERIT_DEFAULT
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.It MAP_INHERIT_COPY
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The child is given a private copy of the region: writes from parent or
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child are not seen by the other.
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.It MAP_INHERIT_NONE
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The region is unmapped in the child.
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.It MAP_INHERIT_SHARE
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The child is shares the region with the parent: writes from parent and
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child are seen by both.
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.It MAP_INHERIT_ZERO
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The region is mapped in the child to anonymous pages filled with
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zeros.
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.El
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.Pp
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Normally, the parent's virtual address space is copied for the child
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as if with
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.Dv MAP_INHERIT_COPY ,
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for which the alias
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.Dv MAP_INHERIT_DEFAULT
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is provided.
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Regions in the parent mapped using
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.Xr mmap 2
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with the
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.Dv MAP_SHARED
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flag are by default shared with the child as if with
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.Dv MAP_INHERIT_SHARED .
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.Pp
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Not all implementations will guarantee that the inheritance characteristic
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can be set on a page basis;
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the granularity of changes may be as large as an entire region.
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.Sh RETURN VALUES
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.Rv -std minherit
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.Sh ERRORS
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.Fn minherit
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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An invalid region or invalid parameters were specified.
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.El
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.Sh SEE ALSO
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.Xr fork 2 ,
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.Xr madvise 2 ,
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.Xr mincore 2 ,
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.Xr mmap 2 ,
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.Xr mprotect 2 ,
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.Xr msync 2 ,
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.Xr munmap 2
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.Sh HISTORY
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The
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.Fn minherit
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function first appeared in
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.Ox 2.0 ,
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then
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.Nx 1.3 .
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.Sh BUGS
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If a particular port does not support page-granularity
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inheritance, there's no way to figure out how large a region is
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actually affected by
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.Fn minherit .
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